1. Field of the Invention
The present invention relates to a method for testing a waterproof casing. Particularly, it relates to a method for testing a waterproof casing element having a flexible waterproofing portion which is compressed against an adjoining element to establish a water tight seal and a stationary watertight portion in which the water tight seal is established by an adhesive.
2 Description of Related Art
To test the water tightness of a waterproof casing element, it is known to immerse the waterproof casing to be tested in a water, so that if there is a portion which is not watertight, air bubbles will appear at the defective portion. In the known method, however, if the camera to be tested is defective in water tightness, internal elements of the camera can be damaged by water which has penetrated through the camera.
To solve the problem mentioned above, a known testing method is used in which internal air pressure of a watertight casing element is reduced, so that the watertightness can be detected in accordance with a change in the internal air pressure. If this testing method is applied to a waterproof casing element having a flexible waterproofing portion, which is compressed against an adjoining element to establish a water tight seal, and a stationary watertight portion, in which the water tightness is established by an adhesive, it is impossible to distinguish between the defective portions. Namely, whether the flexible waterproofing portion is defective or the stationary watertight portion (i.e., the adhesive) is defective cannot be discriminated.
Namely, in the watertight casing of the type mentioned above, upon testing, the internal air pressure thereof is reduced, causing the flexible waterproofing portion to be elastically deformed, thereby establishing an airtight (watertight) connection. If the flexible waterproofing portion has a tiny defective portion (e.g., pin hole), the latter may temporarily disappear when the elastic deformation of flexible waterproofing portion takes place. Namely, there is no air or water leakage through the tiny defective portion which has temporarily disappeared due to the elastic deformation of the flexible waterproofing portion. Accordingly, a defective portion can not be found.
Conversely, when the air pressure reduction is too small to cause a sufficient elastic deformation of the flexible waterproofing portion, if leakage (indicated by a pressure change) takes place, it is impossible to discriminate whether the leakage occurs in the flexible watertight portion or the stationary watertight portion.